1. Field of the Invention
This invention relates generally to centrifugal separators for separating mixed liquids of different densities, and more particularly to an improved separator assembly for achieving higher separation efficiencies with a variety of process liquids.
2. Prior Art
Centrifugal devices are widely used for separating materials of different densities. Such devices have been found to provide a highly satisfactory method of separating liquids from one another based on different weight phases.
Separators, also referred to as extractors, can separate the individual components of a mixed component input stream, provided that the components remain in separate phases. In many instances, extraction may be facilitated with the use of a solvent that is injected into the device as a second input stream. In this case, the device is often referred to as a "contactor" since it brings the waste stream and the solvent stream into intimate contact. The solvent phase, together with the soluble specie(s), is then separated from the carrier phase by differentiation of the phase densities. Typically, the process liquids comprise a lighter (less dense) solvent or organic phase and a heavier aqueous phase, which are introduced into the centrifugal contactor through separate inlets that communicate with a mixing zone. The resulting liquid mixture then enters the rotor of the contactor where centrifugal force separates the heavier phase from the lighter phase by forcing the heavier phase to flow outwardly away from the rotational axis of the rotor and thereby displace the lighter phase closer to the rotational axis of the rotor. The two phases are then individually collected at the upper end of the rotor with the heavier phase exiting at a location adjacent to the outer periphery and the lighter phase exiting at a location adjacent to the rotational axis. Typically, one or both of the exiting phases is subjected to one or more subsequent stages of extraction such as by circulation through another contactor.
A method of centrifugally separating the components of a water-petroleum mixture is described in U.S. Pat. No. 4,959,158 issued to the first-named inventor of this application. The method described therein utilized a centrifugal contactor developed by the U.S. Department of Energy for the extraction of transuranic elements from radioactive waste streams at nuclear processing plants. It was discovered that this device could be advantageously employed for the separation of a water-petroleum mixture. The relatively small size of the device, however, limited the practical applications of the method due to the relatively low throughput. The contactor design did not lend itself to being scaled up in size due to the design of the rotor, which was suspended from the rotor shaft into the contactor chamber. Such design was dictated, in part, by the robotic access to the rotor required in nuclear waste processing applications. In a larger size, a contactor of the same design would be inoperable due to the lack of a lower support for the rotor.
A contactor of a similar design similar to that described above, also developed by the U.S. Department of Energy, is described in U.S. Pat. No. 5,024,647. This contactor also employs a suspended rotor design, which limits its useful size.